The development of tooth whitening techniques has been taking place for well over 100 years. It is well known that the teeth can be effectively bleached by the use of hydrogen peroxide as the bleaching agent, and it is proven that, in general, tooth-whitening preparations having higher concentrations of bleaching agent are more effective in whitening the teeth than those of lower concentrations. Thus, increasing concentrations of the bleaching agent gives rise to a more rapid bleaching action.
A problem with the high concentrations of bleaching solutions is that to perform safe teeth bleaching operations, a “dam” must be prepared to cover the soft tissue in order to keep such insulated and protected from damage as a result of the vigorous oxidative damage that would occur if these concentrated hydrogen peroxide solutions made physical contact with the gingival tissues. Application of concentrated solutions of hydrogen peroxide, without using gel formulations (to provide slower release of lower concentrations of hydrogen peroxide) and a dam (to minimize contact with soft tissues) results in severe discomfort, blistering and tissue injury. Indeed, oral rinse preparations of hydrogen peroxide having concentrations greater than 6% are dangerous for use in the human oral cavity, since exposure of the oral soft tissues for times on the order of seconds, has been demonstrated to cause immediate injury to the gingival and soft tissue of the human oral cavity. The greater the concentration of hydrogen peroxide, the faster and more severe this burning affect to the gingival and soft tissue. This safety issue has been a barrier and a challenge to the development of tooth whitening techniques that employ higher (e.g., greater than 3%) concentrations of hydrogen peroxide.
Besides the tooth whitening effects, hydrogen peroxide has also been used from years as a disinfectant. However, because hydrogen peroxide is considered to be a primary irritant, exposure guidelines are narrow, e.g., the OSHA permissible exposure limit is 1 ppm (eight hour time weighted average) and the NIOSH “immediately dangerous to life and health” limit is 75 ppm. See e.g., http://en.wikipedia.org/wiki/Disinfectant; and “CDC—Immediately Dangerous to Life or Health Concentrations (IDLH): Chemical Listing and Documentation of Revised IDLH Values—NIOSH Publications and Products”. Cdc.gov. 2009 Jul. 31. Retrieved 2012 Nov. 10. Consequently, bottles of hydrogen peroxide solution commercially available to the general public at pharmacies are 3% solutions. Because of the dangers associated with concentrated hydrogen peroxide are well known, the possible benefits of treating the skin or tissues within the oral cavity with higher concentrations of hydrogen peroxide (e.g., above about 3%) remain to be explored.